KVM: s390: Cleanup initial cpu reset

The code seems to be quite old and uses lots of unneeded spaces for
alignment, which doesn't really help with readability.

Let's:
* Get rid of the extra spaces
* Remove the ULs as they are not needed on 0s
* Define constants for the CR 0 and 14 initial values
* Use the sizeof of the gcr array to memset it to 0

Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Link: https://lore.kernel.org/r/20200131100205.74720-3-frankja@linux.ibm.com
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>